1. Field of the Invention
The present invention concerns a turner bar for rotary presses and especially a reversible turner bar for use in two web running directions.
2. Description of the Related Art
The running direction of a substrate web, such as a web of paper, is changed in a rotary press by means of a turner bar. The turner bar is acted upon with compressed air and forms an air cushion at least in some sections of its outer peripheral surface, so that the substrate web does not come into direct contact with the turner bar. This provides several advantages. The friction that arises during the deflection of the substrate web is reduced by the air cushion. The deposition of printing ink on the turner bar is avoided. The printing on the still wet substrate web is not smeared by the turner bar during the deflection of the substrate web. Depending on the printing run, it may be necessary to change the running direction of the substrate web. For example, it may be necessary to deflect a substrate web for one printing run to the right of the web running direction by an angle of, e.g., 90°, and to the left by 90° in another printing run.
To meet these requirements, so-called “flying” turner bars are used in the prior art. For this purpose, the turner bar is detachably mounted in a holder, and a specially manufactured turner bar is necessary for each desired web running direction. In other words, it is necessary to change over from one turner bar to another turner bar that is kept in stock.
Aside from the fact that a separate turner bar must therefore be produced for each web running direction, this solution means increased logistical expense for printing press operators, since turner bars must be stored in the printing plant.
German Patent DE 34 36 870 C1 deals with the aforementioned disadvantages. The early disclosure document discloses a rotatably supported turner bar, in which two pistons, whose geometry corresponds to the edge of the web of paper guided around the outside of the turner bar, are mounted inside the turner bar and are axially displaced by two spindles to close the holes that are not needed in the turner bar.
The design shown in DE 34 36 870 C1 is not very flexible with respect to the web widths to be processed and has fluid-dynamic disadvantages in the formation of the air cushion on the turner bar.